Tuesday, March 20, 2007

Things that go boom in the night

This week I am at a conference on a specific type of supernova, a type astronomers give the exciting name "Type Ia." So, today I'll discuss a bit about why we are having this conference, and over the week I'll try and point out some interesting findings at this meeting.
There are two main types of supernovae. One type occurs when a very massive star at least 8 times heavier than the sun burns its nuclear fuel into iron. Iron cannot be used as fuel, so it builds up until the star collapses on itself, which ignites a supernova explosion.
Type Ia supernovae are different. Stars that don't go supernova as described above form a white dwarf, which is an ultra-dense ball of carbon and oxygen the size of the Earth. It's essentially a giant pile of ash left over from the star's nuclear furnace. Normally, these ashes slowly cool and fade, just like the embers of a dying fire. But in some cases, the white dwarf is somehow made to ignite in a thermonuclear deflagration -- in a matter of seconds, the entire white dwarf fuses carbon into silicon, iron, and nickel, among other metals. These explosions are so bright that they can be seen most of the way across the Universe, billions of light years away.
The problem is, we don't really know how these explosions get started. In the coming days, I'll mention some of the ideas. But none of them really work all that well, which is why we are having the meeting -- to try and make progress in science. Tempers will run high, as this is very controversial stuff. It should be fun!

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The Professor Astronomy Blog is based on work supported by the National Science Foundation under grant no. AST-0602288. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation (NSF).